1. Field of the invention
The present invention relates to a process for the preparation of hydro(halo)fluoroalkanes by starting from the respective hydro(halo)alkenes.
2. The Prior Art.
Hydrofluoroalkanes can be obtained by reduction with LiAlH4 [Ber. 97(7) 1964], or by U.V. irradiation of halofluoroalkanes in the presence of an alcohol (Czech 136,735). However, none of this processes can be applied in industrial operations; because of the high cost of the reactants, or due to the difficulties relating to the equipment required for similar treatments in case of LiAlH.sub.4 ; or due to the use of U.V. light. Moreover, the process of reduction by U.V. is limited, in that by it only a few specific mono- or dihydrogenated on the same carbon atom can be obtained.
In fact, by the said process, the introduction in the molecule of the first hydrogen atom can result relatively simple, even if the reaction times can even be of the order of twenty hours, but the introduction in the molecule of the second hydrogen atom is more difficult than that of the first one, and however no compounds di-hydrogenated on adjacent carbon atoms are obtained.
Also such fluorination processes are known, as the electrofluorination, carried out on hydrocarbons (J. Electrochem. Soc. 95, 47, 1949), but such a process results burdensome as regards the equipment and from the energetic viewpoint; and, above all, side reactions of fragmentation occur. Known are also fluorinations of hydrocarbons carried out with elemental fluorine, generally diluted with nitrogen, in the gaseous phase over Cu/Ag catalyst [Ind. Eng. Chem. 39, 290 (1947)]. However, also such processes are heavily limited in that they lead to the formation of side reaction by-products, such as high amounts of fragmentation products, or dimers and trimers.
Fluorinating halogenated olefins with CoF.sub.3 is known as well [J. Org. Chem. 28, 494 (1963)], but side reactions occur, such as intramolecular H/fluorine, halogen/fluorine substitutions.
Thus, by this process, selectively preparing alkanes from olefins is not possible.
Furthermore, such a fluorination process requires particularly sophisticated equipment withstanding the fluorine used to regenerate CoF.sub.3 (Temperature around 300.degree. C.).